The invention concerns an X-ray optical system with an X-ray source from which X-ray radiation is guided to a sample to be examined, and an X-ray detector for receiving radiation diffracted or scattered from the sample, wherein a beam-guiding X-ray optical element, such as e.g. a collimator, a mono or poly-capillary, an X-ray mirror or a monochromator, is disposed between the source and the sample and/or between the sample and the detector.
X-ray optical systems of this type are realized in almost all conventional X-ray diffractometers, e.g. in “ATX-G optical system”, The Rigaku Journal, Vol. 16, No. 1, 1999, pages 53–58.
X-rays are used to examine the material properties of the most different kinds of samples. They can interact with the atoms of the sample in many ways, wherein part of the impinging rays can be scattered or diffracted in sample-specific spatial directions, or the sample itself can be excited to emit radiation. The products of the interaction can give information about the material properties.
X-ray radiation is thereby usually directed onto the sample surface in the form of a highly spatially confined beam. The beam diameter thereby delimits the sample region from which information is obtained and determines the resolution of the overall X-ray optical system. The beam diameter in the region of the sample is between 500 μm and 50 μm for typical X-ray diffractometers.
Objects under investigation which comprise crystallites (uniformly scattering regions) having a diameter on the order of magnitude of the beam diameter or larger generate discrete intensity maxima in the diffraction patterns in 3-dimensional angular space. Correspondingly large crystallites can occur e.g. in case of abnormal grain growth in metals, or can also be desired products of a production process. For many methods of X-ray analysis, i.e. a simple theta-2theta scan, these discrete intensity maxima can falsify or even completely eliminate diffraction structures due to the random, irregular orientation distributions of the small number of irradiated crystallites in the sample. This phenomenon, called the grain size effect, is generally undesirable. One rather tries to obtain (locally or globally) averaged information about the sample.
To solve this problem, the sample is conventionally ground into a powder thereby reducing the crystallite size which, however, destroys the object under investigation.
In another conventional method, the position of the object under investigation is changed during the measurement, e.g. with a XYZ positioning table. This produces integral information over a larger sample area. This method is not applicable for many objects under investigation since they cannot be moved at all or only very slowly due to their large mass or high sensitivity to acceleration (e.g. for fluids) and therefore a noticeable increase in the swept sample region in reasonable measuring intervals is not possible.
Departing therefrom, it is the underlying object of the present invention to present an X-ray optical system to obtain averaged information about the material sample through X-ray analysis even for investigation of macrocrystalline objects, without destroying or accelerating the object under investigation.